Short-Time Elasticity of Polymer Melts: Tobolsky Conjecture and Heterogeneous Local Stiffness

Abstract

An extended Molecular-Dynamics study of the short-time "glassy" elasticity exhibited by a polymer melt of linear fully-flexible chains above the glass transition is presented. The focus is on the infinite-frequency shear modulus $G_{\infty }$ manifested in the picosecond time scale and the relaxed plateau $G_p$ reached at later times and terminated by the structural relaxation. The local stiffness of the interactions with the first neighbours of each monomer exhibits marked distribution with average value given by $G_{\infty }$. In particular, the neighbourhood of the end monomers of each chain are softer than the inner monomers, so that $G_{\infty }$ increases with the chain length. $G_p$ is not affected by the chain length and is largely set by the non-bonding interactions, thus confirming for polymer melts the conjecture formulated by Tobolsky for glassy polymers.

arXiv comment18 pages, 6 figures

References in corpus (7)

• Amorphous Systems in Athermal, Quasistatic Shear
• Local elasticity map and plasticity in a model Lennard-Jones glass
• The response of disordered matter to electromagnetic fields
• Emergence of rigidity at the structural glass transition: a first principle computation
• Universal divergenceless scaling between structural relaxation and caged dynamics in glass-forming systems
• Weak links between fast mobility and local structure in molecular and atomic liquids
• Cage rattling does not correlate with the local geometry in molecular liquids

Cited by in corpus (2)

• Cage effect in supercooled molecular liquids: local anisotropies and collective solid-like response
• Effect of nematic ordering on the elasticity and yielding in disordered polymeric solids